The invention relates to an inflatable face seal for a respiratory mask such as, for example, an anaesthesia face mask and/or a respiratory face mask. Such face masks are typically used during the medical treatment of patients. The inflatable face seal comprises an annular air-tight hollow portion where a cross section through one section of the annular hollow portion comprises a bonded joint which joins two overlapping flanges.
In typical applications, the inflatable seal of the current invention is used in face masks which consist of a relative stiff shell portion, and an inflatable annular face seal attached to the circumference of the shell via an air tight connection. Such a mask is disclosed in EP 0 602 424. However, the face seal of the current invention could also be used for face masks which consist of a single injection moulded element comprising both a semi rigid shell portion and an inflatable annular face seal in accordance with the current invention.
Such inflatable annular face seals are currently produced in a variety of designs to provide different levels of anatomical fit, ease of use, durability, and ease of cleaning and sterilizing. In addition, during the production of such face seals, it is desired to maintain a low cost of manufacturing.
However the prior art masks can be difficult to manufacture. In particular, since the final mask comprises an annular hollow and air-tight internal portion, the mask cannot be directly formed by an injection moulding or rubber dipping procedure. The masks are therefore usually formed in a two part process where the masks are first moulded using an annular internal core used to form the hollow internal portion. Once the mask is moulded, the mask is stripped from the core via an opening in the mask, the opening being arranged along the circumference of the annular hollow portion. Once the core is removed, then the opening is closed and sealed to form an airtight bonded joint.
The bonded joint is usually made by an adhesive placed between two flanges of the mask. However, since the curing time of the adhesive is usually around one day, a fixture is required to press the two flanges together in order to ensure that the bond is effective. This procedure requires a very large number of fixtures. For example, if the production capacity of the manufacturing operation is 500 masks a day, then at least 500 fixtures are required during the curing process. Acquisition and management of all the fixtures makes the production costs rather expensive and the production process complex.
Furthermore, as EP 0 602 424 shows, the two surfaces which are bonded together are usually arranged as two parallel flanges where the bond is formed between two “inwardly facing” surfaces of the flanges. By inwardly facing is meant surfaces which face in towards the centre of a cross section of a portion of the annular hollow portion. In this way, when pressure is applied to the inner volume of the mask, for example during machine washing and sterilization, the bond is exposed to “peel” forces which attempt to peel the bonded surfaces away from each other. “Peel” forces are hard on the bond since the stresses are applied to the limited area at the inside edge of the bonded joint.
One aspect of the current invention is therefore to provide a design of an inflatable annular face seal which allows the seal to be manufactured at low cost in a variety of elastomeric materials suitable for single use products or reusable products.
Another aspect of the current invention is to provide an inflatable face seal as mentioned in the introductory paragraph which has high durability to repeated use and exposure to cleaning and sterilization procedures.